Pressure-sensing intravascular devices, systems, and methods

ABSTRACT

Intravascular devices, systems, and methods are disclosed. In some embodiments, the intravascular devices include at least one pressure sensing component within a distal portion of the device. In that regard, one or more electrical, electronic, optical, and/or electro-optical pressure-sensing components is secured to an elongated substrate such that the pressure-sensing component is mounted perpendicular to a central longitudinal axis of the device. In some implementations, the elongated substrate has a cylindrical profile. Methods of making, assembling, and/or using such intravascular devices and associated systems are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.14/133,374, filed Dec. 18, 2013, now U.S. Pat. No. ______, which claimspriority to and the benefit of U.S. Provisional Patent Application No.61/745,014, filed Dec. 21, 2012, U.S. Provisional Patent Application No.61/745,493, filed Dec. 21, 2012, and U.S. Provisional Patent ApplicationNo. 61/785,390, filed Mar. 14, 2013, each of which is herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present disclosure relates generally to intravascular devices,systems, and methods. In some embodiments, the intravascular devices areguide wires that include one or more electrical, electronic, optical, orelectro-optical sensors positioned at a distal end.

BACKGROUND

Heart disease is a critical healthcare issue for the individual patientand for society as a whole. Recent research has shown that treatment ofheart disease, when guided by improved diagnostic methods such asfunctional assessment of the coronary circulation using intravascularpressure measurements, leads to both improved quality of life for thepatient and reduced healthcare costs for society.

Intravascular catheters and guide wires are commonly utilized to measurethe pressure within the blood vessel, to visualize the inner lumen ofthe blood vessel, and/or to otherwise obtain diagnostic informationrelated to the blood vessel. To date, guide wires containing pressuresensors, imaging elements, and/or other electrical, electronic, optical,or electro-optical components have suffered from poor mechanicalperformance in comparison to standard guide wires that do not includesuch components. Existing pressure-sensing guide wires typicallyincorporate a single pressure sensor located approximately 3 cm from thedistal tip of the guide wire. Since the sensor is fixed in position onthe guide wire, the pressure can only be measured at different locationswithin the vasculature by advancing or retracting the entire guide wireto position the sensor at the desired location. Traditionally, thepressure-sensing guide wire includes a sensor formed on a planarsubstrate and having terminals attached to the conductors of a cablewhich runs through the intravascular device. The sensor substrate istypically oriented such that the pressure sensitive portion facesradially outward into the blood stream. It is generally desired toseparate the substrate slightly away from the walls of the intravasculardevice in order to mechanically isolate the pressure sensor substratefrom the guide wire structure, so that bending and torsional stressesare not coupled to the sensor substrate where they could adverselyaffect the pressure measurement accuracy. This pressure sensing guidewire geometry provides access for intravascular pressure measurement,but results in compromises to the mechanical structure which lead topoor mechanical performance compared to that of a conventional guidewire without measurement capability. Furthermore, the fragile electricalinterconnects between the sensor terminals and the electrical leads arevulnerable to failure. In this conventional configuration the smalldiameter of the intravascular device introduces places constraints onthe sensor dimensions, exacerbating the limitations and associatedproblems.

Accordingly, there remains a need for improved intravascular devices,systems, and methods that preserve the desirable mechanical propertiesof the device while providing a more robust interconnect to one or moreelectrical, electronic, optical, or electro-optical components.

SUMMARY

According to embodiments disclosed herein an intravascular sensorassembly may include a flexible elongate member having a longitudinalaxis (LA); a core member disposed inside the flexible elongate member;and an elongated substrate disposed distal to the core member and insidethe flexible elongate member, the elongated substrate including at leastone electrode disposed within at least one recess in an outer surface ofthe elongated substrate, the at least one recess extending in alongitudinal direction; and a sensor circuit disposed on a distalsurface of the elongated substrate, the sensor circuit coupled to the atleast one electrode.

In some instances, a pressure-sensing guide wire is provided. Thepressure-sensing guide wire includes a pressure sensor mounted such thata membrane of the pressure sensor extends across a width of the guidewire, instead of along the length of the guide wire. As a result ofmounting the pressure sensor in this orientation, the thickness,robustness, and durability of the pressure sensor can be increased whilestaying within the limited space provided by the outer profile of theguide wire.

According to embodiments disclosed herein a sensor structure for use inan intravascular device assembly may include a substrate having anelongated shape with a length defined along a longitudinal axis (LA) anda width extending perpendicular to the longitudinal axis, the shapefurther including a proximal surface and an opposing distal surface,each extending substantially perpendicular to the LA; and an outersurface extending substantially parallel to the LA between the proximaland distal surfaces; at least one electrode disposed longitudinallywithin at least one recess in the outer surface of the substrate, and asensor circuit disposed on the distal surface, the sensor circuit havingat least one lead or conductor coupled to the at least one electrode.

A system for performing measurements using a sensor exposed to anintravascular environment, the system including an intravascular devicehaving: a flexible elongate member having a longitudinal axis (LA); acore member disposed inside the flexible elongate member; and anelongated substrate disposed distal to the core member and inside theflexible elongate member, the elongated substrate including at least oneelectrode disposed within at least one recess in an outer surface of theelongated substrate, the at least one recess extending in a longitudinaldirection; and a sensor circuit disposed on a distal surface of theelongated substrate, the sensor circuit coupled to the at least oneelectrode; and a control console coupled to the intravascular device.

According to embodiments disclosed herein a method of forming apressure-sensing guide wire may include forming an elongated substrate;forming a plurality of recesses in an outer surface of the elongatedsubstrate; filling at least a portion of each of the recesses with aconductive material to form a plurality of electrodes; fabricating asensor circuit on a front surface of the elongated substrate, the frontsurface extending perpendicular to a longitudinal axis of the elongatedsubstrate; electrically coupling the plurality of electrode to terminalsof the sensor circuit; electrically coupling a plurality of conductorsof a communication cable to the plurality of electrodes; and securingthe elongated substrate to a distal portion of a flexible elongatemember.

These and other embodiments of the present invention will be describedin further detail below with reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, schematic side view of an intravascular deviceaccording to some embodiments.

FIG. 2 is a diagrammatic perspective view of a sensor structureaccording to some embodiments.

FIG. 3 is a diagrammatic partial cross-sectional front view of a sensorstructure according to some embodiments.

FIG. 4 shows a partial perspective view of a distal portion in anintravascular device according to some embodiments.

FIG. 5 shows a partial perspective view of a coupling for an end sensorin a sensor structure according to some embodiments.

FIG. 6 shows a partial schematic view of a system for performingmeasurements using an end sensor exposed to an intravascular environmentaccording to some embodiments.

FIG. 7 shows a flow chart for a method of manufacturing an intravasculardevice having an end sensor, according to some embodiments.

FIG. 8 shows a flow chart for a method of manufacturing an intravasculardevice having an end sensor, according to some embodiments.

FIG. 9 shows a flow chart for a method of obtaining a measurement of anintravascular environment, according to some embodiments.

In the figures, elements having the same reference number have the sameor similar functions.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It is nevertheless understood that no limitation tothe scope of the disclosure is intended. Any alterations and furthermodifications to the described devices, systems, and methods, and anyfurther application of the principles of the present disclosure arefully contemplated and included within the present disclosure as wouldnormally occur to one skilled in the art to which the disclosurerelates. In particular, it is fully contemplated that the features,components, and/or steps described with respect to one embodiment may becombined with the features, components, and/or steps described withrespect to other embodiments of the present disclosure. For the sake ofbrevity, however, the numerous iterations of these combinations will notbe described separately.

As used herein, “flexible elongate member” or “elongate flexible member”includes at least any thin, long, flexible structure that can beinserted into the vasculature of a patient. While each of theillustrated embodiments of the present disclosure includes a flexibleelongate member having a cylindrical form with a circularcross-sectional profile that defines an outer diameter of the flexibleelongate member, in other instances all or a portion of the flexibleelongate member may have other geometric cross-sectional profiles (e.g.,oval, rectangular, square, elliptical, etc.) or non-geometriccross-sectional profiles. Flexible elongate members include, forexample, guide wires and catheters. In that regard, a catheter may ormay not include a lumen extending along its length for receiving and/orguiding other instruments. If the catheter includes a lumen, the lumenmay be centered or offset with respect to the cross-sectional profile ofthe device.

In most embodiments of the present disclosure, the flexible elongatemember includes one or more electrical, electronic, optical, orelectro-optical components. For example, without limitation, a flexibleelongate member may include one or more of the following types ofcomponents: a pressure sensor, a temperature sensor, an imaging element,an optical fiber, an ultrasound transducer, a reflector, a mirror, aprism, an ablation element, an RF electrode, a conductor, and/orcombinations thereof. Generally, these components are configured toobtain data from or deliver therapy to a vessel or other portion of theanatomy in which the flexible elongate member is disposed. Often thecomponents are also configured to communicate with an external devicefor processing, display, activation, and/or control. In some aspects,embodiments of the present disclosure include imaging devices forimaging within the lumen of a vessel, including both medical andnon-medical applications. However, some embodiments of the presentdisclosure are particularly suited for use in the context of humanvasculature. Imaging of the intravascular space, particularly theinterior walls of human vasculature can be accomplished by a number ofdifferent techniques, including ultrasound (often referred to asintravascular ultrasound (“IVUS”) and intracardiac echocardiography(“ICE”)) and optical coherence tomography (“OCT”). In other instances,infrared, thermal, or other imaging modalities are utilized.

The electrical, electronic, optical, and/or electro-optical componentsof the present disclosure are often disposed within a distal portion ofthe flexible elongate member. As used herein, “distal portion” of theflexible elongate member includes any portion of the flexible elongatemember from the mid-point to the distal tip. As flexible elongatemembers can be solid, some embodiments of the present disclosure willinclude a housing portion at the distal portion for receiving theelectrical or electronic components. Such housing portions can betubular structures attached to the distal portion of the elongatemember. Some flexible elongate members are tubular and have one or morelumens in which the electrical or electronic components can bepositioned within the distal portion. In some embodiments, the distalportion does not include a separate housing for mounting the electrical,electronic, optical, and/or electro-optical component(s). In suchinstances, the distal portion may have an outer diameter equal to theouter diameter of the flexible elongate member. In some instances, thedistal portion is coupled to proximal and distal flexible elements(e.g., coils, flexible tubing, etc.). Accordingly, in someimplementations the distal portion includes a step-down outer diameterat each end such that the reduced outer diameter is slightly smallerthan the inner diameter of the proximal and distal flexible elements. Inother implementations, the distal portion has a uniform outer diameterthat is slightly smaller than the inner diameter of the distal andproximal flexible elements.

The electrical, electronic, optical, and/or electro-optical componentsand the associated communication lines are sized and shaped to allow forthe diameter of the flexible elongate member to be very small. Forexample, the outside diameter of the elongate member, such as a guidewire or catheter, containing one or more electrical, electronic,optical, and/or electro-optical components as described herein arebetween about 0.007″ (0.178 mm) and about 0.118″ (3.0 mm), with someparticular embodiments having outer diameters of approximately 0.014″(0.356 mm) and approximately 0.018″ (0.457 mm). In some embodiments, theoutside diameter of the elongate member may have an OD of 0.035″ (0.89mm). As such, the flexible elongate members incorporating theelectrical, electronic, optical, and/or electro-optical component(s) ofthe present application are suitable for use in a wide variety of lumenswithin a human patient besides those that are part or immediatelysurround the heart, including veins and arteries of the extremities,renal arteries, blood vessels in and around the brain, and other lumens.

“Connected” and variations thereof as used herein includes directconnections, such as being glued or otherwise fastened directly to, on,within, etc. another element, as well as indirect connections where oneor more elements are disposed between the connected elements.

“Secured” and variations thereof as used herein includes methods bywhich an member is directly secured to another element, such as beingglued or otherwise fastened directly to, on, within, etc. anotherelement, as well as indirect techniques of securing two elementstogether where one or more elements are disposed between the securedelements.

Sensors used in embodiments consistent with the present disclosure maybe positioned within an intravascular device facing an axial direction.In that regard, some embodiments disclosed herein may generally resembleembodiments disclosed in detail in U.S. patent application Ser. No.11/864,499 entitled “Intravascular Pressure Devices IncorporatingSensors Manufactured Using Deep Reactive Ion Etching,” by Paul DouglasCorl, filed on Sep. 28, 2007, the contents of which are herebyincorporated by reference in their entirety, for all purposes.Furthermore, embodiments consistent with the present disclosure providea robust mounting structure to a pressure sensing circuit facing anaxial direction. Thus relaxing the need for a cantilevered sensordecoupled from external stresses induced by guidewire structures.Embodiments as disclosed herein may include sensor circuits formed on athick wafer substrate that is then disposed on the robust mountingstructure.

Referring now to FIG. 1, shown therein is a portion of an intravasculardevice 100 according to an embodiment of the present disclosure. In thatregard, the intravascular device 100 includes a flexible elongate member102 having a distal portion 104 adjacent a distal end 105 and a proximalportion 106 adjacent a proximal end 107. A component 108 is positionedwithin the distal portion 104 of the flexible elongate member 102proximal of the distal tip 105. Generally, the component 108 isrepresentative of one or more electrical, electronic, optical, orelectro-optical components. In that regard, the component 108 is apressure sensor, a temperature sensor, a flow or velocity sensor, anASIC, a signal conditioning circuit, an RF communication module, amemory module, an imaging element, an optical fiber, an ultrasoundtransducer, a reflector, a mirror, a prism, an ablation element, an RFelectrode, a conductor, and/or combinations thereof. The specific typeof component or combination of components can be selected based on anintended use of the intravascular device. In some instances, thecomponent 108 is positioned less than 10 cm, less than 5, or less than 3cm from the distal tip 105. In some instances, the component 108 ispositioned immediately adjacent to the distal tip 105, and in such case,the distal tip may consist of just a thin coating or may be altogetherabsent. In some instances, the component 108 is positioned within ahousing of the flexible elongate member 102. In that regard, the housingis a separate component secured to the flexible elongate member 102 insome instances. In other instances, the component 108 is integrallyformed as a part of the flexible elongate member 102.

The intravascular device 100 also includes a connector 110 adjacent theproximal portion 106 of the device. In that regard, the connector 110 isspaced from the proximal end 107 of the flexible elongate member 102 bya distance 112. Generally, the distance 112 is between 0% and 50% of thetotal length of the flexible elongate member 102. While the total lengthof the flexible elongate member can be any length, in some embodimentsthe total length is between about 90 cm and about 400 cm, with somespecific embodiments having lengths of 140 cm, 190 cm, or 300 cm.Accordingly, in some instances the connector 110 is positioned at theproximal end 107. In other instances, the connector 110 is spaced fromthe proximal end 107. For example, in some instances the connector 110is spaced from the proximal end 107 between about 0 cm and about 140 cm.In some specific embodiments, the connector 110 is spaced from theproximal end by a distance of 0 cm, 30 cm, or 140 cm.

The connector 110 is configured to facilitate communication between theintravascular device 100 and another device. More specifically, in someembodiments the connector 110 is configured to facilitate communicationof data obtained by the component 108 to another device, such as acomputing device or processor. Accordingly, in some embodiments theconnector 110 is an electrical connector. In such instances, theconnector 110 provides an electrical connection to one or moreelectrical conductors that extend along the length of the flexibleelongate member 102 and are electrically coupled to the component 108.Some specific embodiments of electrical conductors in accordance withthe present disclosure are discussed below in the context of FIGS. 5-11.In other embodiments, the connector 110 is an optical connector. In suchinstances, the connector 110 provides an optical connection to one ormore optical communication pathways (e.g., fiber optic cable) thatextend along the length of the flexible elongate member 102 and areoptically coupled to the component 108. Further, in some embodiments theconnector 110 provides both electrical and optical connections to bothelectrical conductor(s) and optical communication pathway(s) coupled tothe component 108. In that regard, it should again be noted thatcomponent 108 is comprised of a plurality of elements in some instances.In some instances, the connector 110 is configured to provide a physicalconnection to another device, either directly or indirectly. In otherinstances, the connector 110 is configured to facilitate wirelesscommunication between the intravascular device 100 and another device.Generally, any current or future developed wireless protocol(s) may beutilized. In yet other instances, the connector 110 facilitates bothphysical and wireless connection to another device.

As noted above, in some instances the connector 110 provides aconnection between the component 108 of the intravascular device 100 andan external device. Accordingly, in some embodiments one or moreelectrical conductors, one or more optical pathways, and/or combinationsthereof extend along the length of the flexible elongate member 102between the connector 110 and the component 108 to facilitatecommunication between the connector 110 and the component 108.Generally, any number of electrical conductors, optical pathways, and/orcombinations thereof can extend along the length of the flexibleelongate member 102 between the connector 110 and the component 108. Insome instances, between one and ten electrical conductors and/or opticalpathways extend along the length of the flexible elongate member 102between the connector 110 and the component 108. For the sake of clarityand simplicity, the embodiments of the present disclosure describedbelow include three electrical conductors. However, it is understoodthat the total number of communication pathways and/or the number ofelectrical conductors and/or optical pathways is different in otherembodiments. More specifically, the number of communication pathways andthe number of electrical conductors and optical pathways extending alongthe length of the flexible elongate member 102 is determined by thedesired functionality of the component 108 and the correspondingelements that define component 108 to provide such functionality.

Embodiments consistent with the present disclosure may provide theability to extend or retract a sensor to multiple locations along thelength of the intravascular device—or to expose a fixed sensor topressures from axially disparate locations by extending or retracting a“snorkel”. For example, in some implementations the sensor may besecured to a central core that is mechanically translatable relative toa surrounding elongate member. In embodiments where the sensor is apressure sensor, blood pressure along the vessel may be mapped withoutmoving the distal tip position of the intravascular device. The distaltip position may remain fixed with the exterior elongated member 130while the sensor is pulled back with core member 135. Furthermore, anengagement feature of the sensor structure 108 or other associatedcomponent may enable torque and rotation of the tip of the wire, ifdesired. Such embodiments having a pullback capability may be asdisclosed in U.S. Provisional Patent Application No. 61/746,537 entitled“Pressure Guide Wire with Sliding Pressure Sensor,” filed Dec. 27, 2012,the contents of which are herein incorporated by reference in theirentirety, for all purposes. Further, some embodiments include featuresof the devices disclosed in U.S. Provisional Patent Application No.61/747,958 entitled “Intravascular Devices Having Artificial Muscles andAssociated Systems, and Methods,” filed Dec. 31, 2012, the contents ofwhich are herein incorporated by reference in their entirety, for allpurposes.

FIG. 2 is a diagrammatic perspective view of sensor structure 108 for anend sensor 220 according to some embodiments. Sensor structure 108includes a substrate 210 having a substantially cylindrical shape in theillustrated embodiment. Substrate 210 includes a distal surface 211 anda proximal surface 212, a diameter D 215 and a length L 216.Accordingly, L 216 may be as thin as 0.001 mm, or 1, 2, 3, 5 mm, or evenlonger, with some embodiments being about 0.1 mm, and other embodimentsbeing about 0.5 mm. In some embodiments it is desirable to have ashorter L 216 to reduce impact on a bending stiffness. Embodiments usinglonger L 216 may include a robust protection to avoid bending. Bendingis not desirable as it may break the coupling to the sensor or thesensor itself, with potential loss of signal. Accordingly, it isdesirable to have an aspect ratio defined as length over diameter ofless than approximately 2. For example, in an embodiment of a 0.014″(0.356 mm) diameter guide wire, where the component 108 may have adiameter of approximately 0.010″ (0.25 mm), length L 216 may be as shortas 0.020″ (0.50 mm), or even less. Diameter D 215 may have a reduceddimension in order for sensor structure 108 to fit within intravasculardevice 100. In some implementations, the sensor structure 108 has adiameter D 215 that is sized to fit within a housing. For example, insome implementations the sensor structure is disposed within a housinghaving an opening through a sidewall to expose the sensor structure toambient. In some particular embodiments, the housing containing thesensor structure is positioned between two flexible members (e.g.,coils, polymer tubes, coil-embedded polymer tubes, and/or combinationsthereof). The sensor structure 108 may be secured to the housing usingany suitable techniques, including adhesive. For example, in someinstances the sensor structure 108 is mounted lengthwise within ahousing similar to that described in U.S. Pat. No. 7,967,762 entitled“Ultra Miniature Pressure Sensor,” the contents of which are hereinincorporated by reference in their entirety, for all purposes.Accordingly, in some embodiments diameter D 215 may be 2 mm, 1 mm, 500μm, or less. For example, for guide wires having an OD of about 0.0145″(0.37 mm), D 215 may be smaller than about 0.0115″ (0.29 mm). For guidewires having an OD of about 0.018″ (0.46 mm), D 215 may be as large as0.0145″ (0.37 mm). And for guide wires having an OD of about 0.035″(0.89 mm), D 215 may be as large as 0.030″ (0.76 mm). This technology isparticularly suitable for the severely space constrained geometries ofsmaller guide wires.

Substrate 210 may be made of silicon or any other material used in asemiconductor foundry, such as germanium, silica, quartz, glass,sapphire, or any ceramic material. Substrate 210 includes electrodes230-1, 230-2, and 230-3 (collectively referred to hereinafter aselectrodes 230). In some embodiments electrodes 230 include conductorsformed of gold, silver, copper, aluminum, or any other conductingmaterial. In some embodiments, the end sensor 220 includes a flexiblemembrane positioned over a cavity such that the flexible membrane sealsthe cavity. The applied pressure causes the membrane to deflect into thecavity in varying amounts. In some instances, the membrane is embeddedwith conductive materials that are patterned to form a piezoresistive,capacitive, nanowire, nanofiber, and/or other suitable pressuretransducing circuit elements. Accordingly, the pressure applied to themembrane causes the membrane to flex, which causes the embedded circuitto change resistance, capacitance, and/or other measurablecharacteristic that can be correlated to the applied pressured. Themembrane may have a square, rectangular, circular, elliptical, othergeometrical, and/or non-geometrical shape.

End sensor 220 is coupled to electrodes 230 by conductors 235-1, 235-2,and 235-3 (collectively referred to hereinafter as conductors 235).Conductors 235 may be electrically conductive wires, conductive traces,or doped semiconductor materials. Electrodes 230 may be formed withinvias etched through a silicon substrate (e.g., cylindrical substrate210) using semiconductor manufacturing techniques. In other embodiments,the electrodes 230 are formed in recesses formed in an outer surface ofthe silicon substrate. Accordingly, electrodes 230 are disposedlongitudinally, either through the substrate 210 or along a surface ofthe substrate 210, in a direction that is parallel to the LA.

In some instances, each electrode 230 has a proximal end adjacent to orat proximal surface 212 and an opposing distal end adjacent to or atdistal surface 211. In other instances, the proximal end of eachelectrode is spaced distally from the proximal surface 212. In thatregard, by keeping space within the through vias and/or the recesses inthe outer surface of the substrate 210, conductors that are to beelectrically coupled to the electrodes 230 can be at least partiallypositioned within the through vias and/or recesses where they areelectrically coupled to the electrodes. For example, in some instancesdistal sections of the conductors are positioned within the through viasand/or recesses such that distal ends of the conductors are positionedadjacent to and/or in contact with proximal ends of the electrodes. Thensolder, welding, and/or other suitable conductive coupling mechanism isutilized to secure and electrically couple the conductors to theelectrodes.

End sensor 220 is disposed on distal surface 211, facing outwards, inthe distal direction. Embodiments consistent with this configurationreduce the constraint for having a thin sensor layer in a cantileveredconfiguration. Further, the mechanical robustness of substrate 210relieves sensor 220 from stress in the core wire and/or other portionsof the guide wire. In addition, since distal surface 211 is aligned in adirection substantially parallel to a torque rotating core member 135about the LA, sensor 220 is decoupled from stresses arising fromtorsional effects. Such configuration reduces design concerns about thefabrication process of sensor circuit 220, relaxing geometrical andmechanical constraints.

In some embodiments, sensor 220 includes circuits and structures such asa micro-electromechanical system (MEMS), formed on a wafer. In someembodiments, end sensor 220 may be formed using semiconductormanufacturing techniques such as etching, deposition, and implantationof conductive layers on a substrate. When sensor 220 faces the distaldirection, sensor 220 may have a thickness that reduces limitations tothe placement of intravascular device 100 within a blood vessel. Thus,the wafer used for making sensor 220 may be a thin wafer (approximately50 to 100 μm), an ultra-thin wafer (less than 50 μm and as thin as 1μm), or a wafer of regular thickness (typically 300 to 700 μm). Forexample, in some embodiments the entire component 108 including sensor220 may be formed on a 400 to 600 μm thick wafer which also providessubstrate 210, and include electrodes 230 formed in vias through thewafer. In this context, the generally cylindrical cross-sectionalprofile of the component 108 is produced by an etching process such asdeep reactive ion etching. In the case where the cross-sectional profileintersects one or more of the through wafer vias, those vias becomerecesses in the surface of the substrate 210. Accordingly, sensor 220may include a circuit and/or structure such as a MEMS manufactured usinga Deep Reactive Ion Etching (DRIE) technique, as disclosed in detail inU.S. patent application Ser. No. 11/864,499, entitled “IntravascularPressure Devices Incorporating Sensors Manufactured Using Deep ReactiveIon Etching,” filed Sep. 28, 2007, the contents of which areincorporated herein by reference in their entirety, for all purposes.

FIG. 3 is a diagrammatic end view of a sensor structure 308 for endsensor 220 according to some embodiments. Accordingly, sensor structure308 includes substrate 210 having a substantially cylindrical shape.Also, sensor structure 308 includes electrodes 330-1, 330-2, and 330-3(collectively referred hereinafter as electrodes 330). Electrodes 330are coupled to end sensor 220 through conductors 335-1, 335-2, and335-3, respectively (hereinafter referred to as conductors 335).Conductors 335 may be as conductors 235 described in detail above (cf.FIG. 2). Accordingly, electrodes 330 may be formed as indentions onsubstrate 210 with a conductive material deposited to fill in thestructure, forming an approximately cylindrical shape. Furthermore,electrodes 330 may extend from a distal surface of sensor structure 308(the surface including sensor 220) to a proximal surface of sensorstructure 308, opposite the distal surface. In some implementations, thesensor structure 308 is coated with an insulating material afterformation of the electrodes 330 and/or electrically coupling of theelectrodes 330 to conductors of a communication cable.

FIG. 4 shows a partial perspective view of a distal portion 406 of anintravascular device 400 according to some embodiments. Distal portion406 of intravascular device 400 may include elements as distal portion106 of intravascular device 100 described in detail above (cf. FIG. 1).For example, distal portion 406 includes sensor structure 108 havingsensor 220 on a distal surface. In addition, distal portion 406 includesa portion of elongate flexible member 430 having holes 435-1 and 435-2(collectively referred hereinafter as holes 435). Holes 435 exposesensor 220 to ambient fluid such as blood and other fluids presentinside the blood vessel. Generally, the holes or openings 435 may haveany shape, including geometrical (e.g., oval, circular, ellipse,rectangle, triangle, square, rhombus, etc.), non-geometrical, and/orcombinations thereof. Likewise, the intravascular device 400 may includeany number of openings to facilitate exposing the sensor 220 to thesurrounding ambient fluid. In that regard, the number of openings may bedependent on the size and/or positioning of the openings.

FIG. 4 shows distal end 405 which may be as distal end 105 described indetail above (cf. FIG. 1). In addition, distal end 405 may have atapered shape, as illustrated in FIG. 4. One of ordinary skill willrecognize that the specific shape of distal end 405 is not limiting anda straight shape may be used for distal end 405. In some embodiments,the distal end 405 is closed. In other embodiments, the distal end 405is open such that it provides a further passageway to expose the sensor220 to the surrounding ambient fluid within the vessel.

FIG. 5 shows a partial perspective view of a coupling for an end sensorin sensor structure 108 according to some embodiments. Accordingly, thecoupling in FIG. 5 forms an interface between core member 135 and sensorstructure 108. FIG. 5 illustrates a cable 501 including three wires, orconductors. Cable 501 may be a trifilar cable as described in detail inU.S. Provisional Patent Application No. 61/665,697, filed Jun. 28, 2012,and entitled “Intravascular Devices, Systems, and Methods,” the contentsof which are incorporated herein by reference in their entirety, for allpurposes.

Cable 501 is separated into leads adjacent a distal surface of coremember 135 facing a proximal surface 212 of sensor structure 108. Insome embodiments, cable 501 includes electrical conductors or wiresforming leads 510-1, 510-2, and 510-3 (collectively referred hereinafteras leads 510) that may be placed on a distal surface of core member 135.Thus, leads 510 end in a dot of solder material to make electricalcontact with electrodes 230 in sensor structure 108 in some instances.In other instances, the leads 510 are at least partially positionedwithin the openings or recesses in which the electrodes 230 of thesensor structure 108 are formed. In some instances, a distal surface ofthe core member 135 and a proximal surface of the sensor structure 108are abutted against each other. In some embodiments, sensor structure108 may be glued to core member 135 using an adhesive or glue. In someembodiments, the adhesive may be urethane acrylate, cyanoacrylate,silicone, epoxy, and/or combinations thereof; the adhesive is selectedto secure sensor structure 108 to core member 135. In some instances,the sensor structure 108 is flexibly connected to the core member 135.In yet other instances, the sensor structure 108 is not secured to thecore member 135, but instead is held in place by attached conductivewires.

Embodiments consistent with the present disclosure provide a robustinterconnect between cable 501 and electrodes 230. For example, as shownin FIG. 5 the electrical contact is sandwiched between a distal surfacein core member 135 and proximal surface 212 in sensor structure 108.Furthermore, the interconnect configuration for sensor circuit 220 isfully within the flexible elongate member 102 of intravascular device100, thus adding no extra constraints for device geometry. Theconductors may take any suitable form, including without limitationflex-foil, spiral wrapped, direct-write, wound wires, and/orcombinations thereof.

FIG. 6 shows a partial schematic view of a system 600 for performingmeasurements using an end sensor exposed to an intravascular medium.System 600 includes an intravascular device 100; an interface device 610coupled to the intravascular device; a control console 620 including aprocessor circuit 621; and a display unit 630. The intravascular device100 may be similar to those described above, including having a sensorstructure similar to those described above.

Interface device 610 may include electronic circuits configured toprovide power and signals to sensor circuit 220. Electronic circuits ininterface device 610 may also be configured to receive and processsignals from sensor circuit 220. For example, interface device 610 mayinclude an analog-to-digital converter, enabling interface device 610 toperform analog-to-digital conversion of signals provided by sensorcircuit 220. Console 620 may control the operation of interface device610 by providing power and receiving the sensor circuit data processedby interface device 610. Once the data is processed and further analyzedin console 620, an image may be displayed on display unit 630. Forexample, an image may include a graphic display and charts representingpressure values along a longitudinal direction in a blood vessel.

FIG. 7 shows a flow chart for a method of manufacturing an intravasculardevice having an end sensor, according to some embodiments. Steps inmethod 700 may be performed manually by an operator, or automatically bya machine controlled by a computer having a processor circuit and amemory circuit. Further, according to some embodiments, steps in method700 may be partially performed by an operator and some steps may bepartially performed automatically by a machine controlled by a computer.The intravascular device in method 700 may be similar to one or moreembodiments described in the present application. In some instances, theintravascular device includes a core element, a sensor structure for asensor, and a flexible member. Furthermore, the intravascular device ofmethod 700 may include a cable extending along the core member toprovide power and collect data from the sensor (e.g., cable 501).

In some aspects, the end sensors of the present disclosure rely uponmanufacturing techniques similar to those used for existing products,but with some important differences. One particular important differenceis that the end sensor is not thinned in the manner of existingproducts. For example, in some implementations existing products removeback-side material of a wafer until the thickness of the resultingsensor device is ˜0.050-0.075 mm. A thin sensor device is important insome existing products because the device is placed in a horizontalorientation (with the membrane facing parallel to the longitudinal axis)and must fit within the 0.356 mm diameter constraint of the guide wiresin which they are utilized. By placing the sensor with the membranefacing perpendicular to the longitudinal axis—toward the distal (orproximal) end of the guide wire in accordance with the presentdisclosure, the length or thickness of the sensor can be optimized forstrength, flexibility, connectivity, and/or combinations thereof.

In step 710 a substrate is formed in an elongated shape. Accordingly,the elongated shape is substantially cylindrical in some instances, witha longitudinal axis parallel to the LA of the intravascular device, anda front surface substantially perpendicular to the LA. However, thesubstrate may have other elongated shapes in other implementations,including elongated shapes having cross-sectional profiles that aregeometrical, non-geometrical, and/or combinations thereof. The frontsurface is formed substantially planar with a circular cross-sectionalprofile in some instances. In some embodiments, step 710 includesforming an elongated substrate having a length of a few mm, such as 1,2, 3, 5 mm, or even longer. In some embodiments it is desirable to havea shorter length to reduce impact on a bending stiffness. Embodimentsusing longer length may include a robust protection to avoid bending.Bending is not desirable as it may break the coupling to the sensor orthe sensor itself, with potential loss of signal. Accordingly, it isdesirable to have length as short as 0.020″ (0.50 mm), or even less.Step 710 may include forming an elongated substrate having across-sectional profile (e.g., a cylindrical shape with a circularcross-sectional profile having a diameter) with a width or diameter ofabout 2 mm, 1 mm, 500 μm, or less. For example, for wires having an ODof about 0.0145″ (0.37 mm), the diameter may be smaller than about0.0115″ (0.29 mm). For wires having an OD of about 0.018″ (0.46 mm), thediameter may be as large as 0.0145″ (0.37 mm). And for wires having anOD of about 0.035″ (0.89 mm), the diameter may be as large as 0.030″(0.76 mm). In some embodiments step 710 may include forming a substratefrom silicon, germanium, or an alloy of silicon and germanium, usingsemiconductor fabrication techniques. Materials used in step 710 maydepend on the specific application and are not limiting of embodimentsconsistent with the present disclosure. In general, materials used instep 710 may be any material used in a semiconductor foundry, such assilica, quartz, glass, sapphire, any ceramic material, or even a plasticsuch as vinyl.

In step 720 through holes and/or recesses are formed in the substrate.In some embodiments, step 720 may include etching through holes parallelto the LA of the elongated substrate in step 710. Accordingly, step 720may include forming holes as through silicon vias in an elongatedsilicon substrate provided in step 710. In some embodiments, step 720may include forming longitudinal notches or indentations on a sidesurface of the elongated substrate in step 710. In some embodiments,step 720 may be performed using semiconductor fabrication techniquessuch as ion beam bombardment. In some embodiments, step 720 may includeforming a micro-extrusion in the substrate and subsequently attachingthe extruded portion to a functional cap.

In step 730 the through holes and/or recesses formed in step 720 are atleast partially filled with a conductive material to form electrodes.Step 730 may include techniques such as flowing, sputtering, and/orvapor deposition of a conductive material inside the through holesand/or recesses formed in step 720. Step 730 may include using aconductive material such as gold, silver, copper, aluminum, an alloy ofthe above, or any combination of the above to at least partially fillthe through holes and/or recesses.

In step 740 a sensor circuit is formed on a wafer substrate. Forexample, step 740 may include a DRIE process to form a MEMs circuit on asubstrate. In some instances, an off-the-shelf pressure sensor isprovided. In some instances, a pressure sensor diaphragm and resistorarrangement similar to that described in U.S. Pat. No. 7,967,762,entitled “Ultra Miniature Pressure Sensor,” is utilized.

In step 750 the sensor circuit is placed on the front surface of theelongated substrate. Accordingly, step 750 may include using an adhesiveto securely place the sensor circuit on the elongated substrate. In someembodiments, step 750 may include bonding the sensor circuit on thefront surface of the elongated substrate using semiconductormanufacturing techniques, such as flip-chip techniques. The frontsurface of the elongated substrate in step 750 may be a surfacesubstantially perpendicular to the LA of the elongated substrate.

In step 760 conductors are formed joining the electrodes to the sensorcircuit terminals. In some embodiments, step 760 may include formingconductors using semiconductor manufacturing techniques for depositingconducting elements along a track. In some embodiments, step 760 mayinclude depositing semiconductor materials and dopants along trenches inthe front surface of the elongated substrate. The tracks or trenchesused in step 760 may join the electrodes formed in the elongatedsubstrate to the sensor circuit terminals. Step 760 may includeperforming procedures used in the semiconductor manufacturing industrysuch as photolithography and DRIE. Step 760 includes forming tracks andtrenches on the elongated substrate and depositing materials on thetracks and in the trenches. Ion beam deposition, sputtering, vapordeposition, and annealing are procedures that may be included in step760, according to some embodiments.

In step 770 cable leads are electrically coupled to the electrodesformed in step 730. Step 770 may include forming bonds on a back surfaceof the elongated substrate including the electrodes. The back surfacemay be substantially perpendicular to the LA of the elongated substrate,and opposite to the front surface having the sensor circuit according tostep 750. Cable leads in step 770 may include three wires, eachconnected to a separate node of the circuit. For example one wire may beconnected to the ground node of the measurement circuit, while the othertwo wires may be connected to signal nodes which carry electricalsignals representing the measurement of interest, such as pressure.

In step 780 the elongated substrate is bonded to the core member orother structure of the intravascular device. Accordingly, step 780 mayinclude bonding a distal surface in the core member to a proximalsurface in the elongated substrate using an adhesive. The proximalsurface in the elongated substrate may be the back substrate havingbonds to the electrodes as in step 770. In some instances, the elongatedsubstrate is bonded to a component or components of the intravasculardevice other than the core member, such as a housing, a flexible element(e.g., coil, polymer tubing, coil-embedded polymer tubing, etc.), orotherwise.

FIG. 8 shows a flow chart for a method of manufacturing an intravasculardevice having an end sensor, according to some embodiments. Steps inmethod 800 may be performed manually by an operator, or automatically bya machine controlled by a computer having a processor circuit and amemory circuit. Further according to some embodiments some steps inmethod 800 may be partially performed by an operator and some steps maybe partially performed automatically by a machine controlled by acomputer. The intravascular device in method 800 may include featuressimilar to the intravascular devices described above.

In step 810 a sensor circuit is formed on a substrate surface. Also instep 810, the substrate is bonded to a core member, housing, flexibleelement (e.g., coil, polymer tubing, coil-embedded polymer tubing,etc.), and/or other element to form an intravascular device, such as aguide wire. Accordingly, in some embodiments step 810 may includeperforming one or more of steps 710 through 780 in method 700, asdescribed in detail above.

In step 820 the core member is disposed inside a flexible member of theintravascular device. In step 830 one or more through holes or openingsare formed in a distal portion of the flexible member of step 820. Forexample, the through holes may be through a side wall of the flexiblemember, through a side wall of a housing, and/or other portion of theflexible member to expose the sensor circuit of step 810 to ambient(e.g., through holes 435, cf. FIG. 4).

FIG. 9 shows a flow chart for a method 900 of obtaining a measurement ofan intravascular environment, according to some embodiments. Method 900may be partially performed by an operator using a system for performingmeasurements with an end sensor exposed to an intravascular environment,such as system 600 described in detail above (cf. FIG. 6).

In step 910 the intravascular device is disposed at a position inside ablood vessel. In step 920 a power is provided to a sensor circuit in theintravascular device, wherein the sensor circuit is disposedsubstantially perpendicular to a longitudinal axis of the intravasculardevice (e.g., sensor circuit 220, cf. FIG. 2). In some embodiments, step920 may include providing a voltage to a cable running along theintravascular device (e.g. cable 501, cf. FIG. 5). Further according tosome embodiments, step 920 may include providing an optical signal to anoptical fiber in a cable running along the intravascular device. To thatend, in some instances the pressure sensor is an optical pressure sensoras disclosed in one or more of U.S. Pat. No. 7,689,071, entitled “FIBEROPTIC PRESSURE SENSOR FOR CATHETER USE,” U.S. Pat. No. 8,151,648,entitled “ULTRA-MINIATURE FIBER-OPTIC PRESSURE SENSOR SYSTEM AND METHODOF FABRICATION,” U.S. application Ser. No. 13/415,514, entitled“MINIATURE HIGH SENSITIVITY PRESSURE SENSOR,” each of which isincorporated by reference in its entirety, for all purposes.Accordingly, step 920 may be performed by the control console throughthe interface device.

In step 930 a signal from the sensor circuit is received. For example,the signal may be received in the interface device. In step 940 thesignal from the sensor circuit is processed. For example, in someembodiments an analog signal may be converted to a digital signal in theinterface device. In step 950 a measurement from the intravascularenvironment is formed. Accordingly, step 950 may be partially performedusing the processor circuit and the memory circuit in the controlconsole. In some embodiments, step 950 may include storing the processedsignal from the sensor circuit and/or storing the position of theintravascular device inside the blood vessel. For example, the processedsignal and the associated position of the intravascular device may bestored in the memory circuit in the control console in some instances.In some embodiments, step 950 may include displaying the measurement inthe display unit. In step 960 the intravascular device is displaced to adifferent position and another measurement is obtained by repeating oneor more of steps 920, 930, 940, and 950.

Embodiments of the invention described above are exemplary only. Oneskilled in the art may recognize various alternative embodiments fromthose specifically disclosed. Those alternative embodiments are alsointended to be within the scope of this disclosure. As such, theinvention is limited only by the following claims.

What is claimed is:
 1. A system, comprising: a sensing guidewire,comprising: a flexible elongate member configured to be positionedwithin a blood vessel of a patient, the flexible elongate membercomprising a proximal portion and a distal portion; a core wire disposedwithin the flexible elongate member; a first electrical conductorextending along a length of the flexible elongate member from theproximal portion to the distal portion; and a sensor assembly disposedat the distal portion of the flexible elongate member, wherein thesensor assembly comprises: a semiconductor substrate comprising adifferent, second electrical conductor in communication with the firstelectrical conductor; and a physiological sensor disposed on a surfaceof the semiconductor substrate, wherein the physiological sensorcomprises at least one of a pressure sensor or a flow sensor, whereinthe physiological sensor is in communication with the first electricalconductor via the second electrical conductor.
 2. The system of claim 1,wherein the sensor assembly further comprises at least one of anapplication specific integrated circuit (ASIC), a signal conditioningcircuit, an RF communication module, or a memory module.
 3. The systemof claim 1, wherein semiconductor substrate comprises an elongatedcylinder.
 4. The system of claim 3, wherein physiological sensor isdisposed a distal end surface of the elongated cylinder.
 5. The systemof claim 3, wherein the first electrical conductor and the secondelectrical conductor are coupled at a proximal end surface of theelongated cylinder.
 6. The system of claim 3, wherein the secondelectrical conductor extends longitudinally from a distal end surface toa proximal end surface of the elongated cylinder.
 7. The system of claim1, wherein physiological sensor is a disposed on a forward-facingsurface of the semiconductor substrate.
 8. The system of claim 1,wherein the semiconductor substrate comprises at least one of silicon,germanium, a silicon-germanium alloy, silica, quartz, sapphire, aceramic material, or a plastic material.
 9. The system of claim 1,wherein the semiconductor substrate is bonded to at least one of theflexible elongate member or the core wire using an adhesive.
 10. Thesystem of claim 1, wherein the flexible elongate member comprises a holeconfigured to expose the physiological sensor to blood within the bloodvessel.
 11. The system of claim 1, further comprising: a control consolein communication with the sensing guidewire.
 12. The system of claim 11,further comprising: an interface device communicatively disposed betweenthe control console and the sensing guidewire, wherein the interfacedevice configured to provide power to the physiological sensor andprocess a signal from the physiological sensor.
 13. The system of claim12, wherein the interface device comprises an analog to digitalconverting circuit configured to provide a digital signal to the controlconsole.
 14. The system of claim 11, wherein the control console isconfigured to output a visual representation of data obtained by thephysiological sensor.
 15. The system of claim 1, wherein thephysiological sensor comprises a micro-electromechanical system (MEMS)sensor.
 16. The system of claim 1, wherein the physiological sensorcomprises an ultrasound transducer.
 17. The system of claim 1, whereinthe physiological sensor is flip-chip bonded to the surface of thesemiconductor substrate.